The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs, and, for these advances to be realized, similar developments in IC manufacturing are needed.
As merely one example, interconnects, the conductive traces used to carry electrical signals between the elements that make up the circuit, are typically embedded in insulating material. Historically, this insulating material has been silicon dioxide. However, the relative permittivity (or dielectric constant) of silicon dioxide, a measure of the insulating properties, is relatively high. Certain low-k materials, with a dielectric constant lower than that of silicon oxide, have been suggested for replacing silicon dioxide and providing a dielectric material having a lower relative permittivity that can reduce interference, noise, and parasitic coupling capacitance between the interconnects. In fact, one manner of providing insulating properties with low relative permittivity is forming an air gap, as air has a low dielectric constant. However, fabrication processes for creating an air gap structure and air gap structures themselves, although existing in some embodiments that are generally adequate, they have not proved entirely satisfactory in all respects.